The present invention relates to a manufacturing method for a gas discharge panel that is composed by attaching a first substrate to a second substrate. More specifically, the present invention relates to a manufacturing method and a manufacturing apparatus for the gas discharge panel, which are characterized by an atmosphere for keeping the both substrates in an alignment step and in the preceding step.
Conventionally, an AC plasma display panel (hereafter called xe2x80x9cPDPxe2x80x9d) shown in FIG. 8 is known as one example of gas discharge panels. This figure shows a construction of a part of the PDP in perspective view, with certain parts omitted.
The PDP includes an envelope 12 that is composed of a first substrate 5 and a second substrate 10 which are opposed to each other and whose periphery is sealed with a seal member 11 consisting of a low melting glass. The first substrate 5 is formed with a plurality of display electrodes 2, a dielectric layer 3, and a protective layer 4 which are formed on the internal surface of a glass substrate 1. The second substrate is formed with a plurality of data electrodes 7 extending orthogonally to the display electrodes 2, a dielectric layer. 8 which are formed on the internal surface of a glass substrate 6. In addition, a plurality of partition walls 9 consisting of a low melting glass are formed at equal spaces and in parallel on the dielectric layer 8 in order to divide an internal space between the two substrates into a light-emitting cell.
Also, a phosphor 13 is applied onto the dielectric layer 8 for each light-emitting cell divided by the partition walls 9 in order to display a color image, and a discharge gas consisting of a mixture of Ne and Xe is enclosed in the envelope 12 with approximately 66,500 Pa of pressure.
In general, the PDP is manufactured by attaching the first substrate 5 to the second substrate 10 which are fabricated by separate steps. The first substrate 5 is prepared in the following manner: that is, the display electrodes are formed on the glass substrate, and a dielectric is applied thereon as a layer and baked. Finally, a film consisting of MgO or the like as the protective layer is formed on the dielectric layer according to an electron-beam evaporation (EB evaporation) method or the like to complete the first substrate 5.
Meanwhile, the second substrate 10 is prepared in the following manner: that is, the data electrodes are formed on a glass substrate, a dielectric is applied thereon as a layer, and the partition walls consisting of a low melting glass are formed in a predetermined pattern. Next, phosphors are applied as a layer between partition walls. Finally, the seal member (normally consisting of a mixture of a flit glass and a binder) is applied onto the periphery of the glass substrate, and pre-baking is performed for driving off the binder included in the seal member to complete the second substrate.
Then, the first substrate and the second substrate fabricated as above are arranged and fixed at predetermined locations with contacting each other, while being heated and sealed to complete the envelope.
Finally, after an internal space within the envelope is evacuated, the space is heated at a predetermined temperature. Then, the discharge gas is enclosed in the space to complete the gas discharge panel.
Here, some finished PDPs which are manufactured by the above-mentioned steps have problems of increase in a discharge starting voltage, generation of an abnormal discharge phenomenon during light-emitting, and so on. These problems result from the following reasons.
Firstly, the MgO layer formed on the first substrate as the protective layer is made up of a plurality of needle shaped molecules which are arranged systematically and substantially vertical to the glass substrate. As such, if water or gaseous molecules are absorbed into these molecules, then it is difficult to remove the water or the gaseous molecules from there.
In the finished panel, the protective layer is exposed to discharge, so that the temperature of the layer becomes high. As a result, the water or the gaseous molecules gradually leak out to the discharge space, which deteriorates the degree of purity of the discharge gas.
Secondly, phosphors formed on the second substrate have an extremely porous structure. Thus, water or gaseous molecules are absorbed into the phosphors as well as the protective layer.
It can be considered that such a deterioration of the degree of purity of the discharge gas causes the above-mentioned problems of increase in the discharge starting voltage and generation of the abnormal discharge phenomenon. Naturally, it is preferable to remove both water and gaseous molecules. However, it is known that effects can be obtained when water only is removed. Therefore, it is preferable that the first substrate after forming a protective layer thereon and the second substrate after a pre-baking of the seal member are not exposed to the air as much as possible. However, it is the current state of the art that such a consideration is not given in the actual PDP manufacturing step.
The object of the present invention is therefore to provide a manufacturing method and a manufacturing apparatus for a gas discharge panel to avoid degradation of the panel properties due to deterioration of the degree of purity of the discharge gas and therefore realize excellent panel properties.
The object can be achieved by a manufacturing method for a gas discharge panel that has a first substrate on which a protective layer is formed and a second substrate on which phosphor layers are formed, and the manufacturing method includes an alignment step for arranging the first substrate and the second substrate at predetermined locations, while opposing the first substrate and the second substrate, wherein the alignment step is conducted under a reduced pressure.
Such an alignment step conducted under a reduced pressure leads to reduction in the amount of water and gaseous molecules which are confined in the internal space in the alignment step, which suppresses problems of increase in the discharge starting voltage and generation of the abnormal discharge phenomenon and therefore realizes excellent panel properties. By the way, the internal space in the finished panel is filled with a discharge gas. Prior to the gas filling step and after the sealing step, it is difficult to effectively exhaust impurities such as water vapor from the space. Especially, when the alignment step is conducted in the air where the content of water vapor is not controlled, the difficulty becomes remarkable. However, the alignment step conducted under a reduced pressure according to the invention can reduce the amount of water vapor which is confined in the internal space in the alignment step. Therefore, a gas discharge panel having excellent panel properties can be obtained.
In addition, in the above manufacturing method, the first substrate is placed under a reduced pressure and heated in a first reduced pressure chamber and/or the second substrate is placed under a reduced pressure and heated in a second reduced pressure chamber, prior to the alignment step in which the first and the second substrates are aligned under a reduced pressure in a third reduced pressure chamber.
As stated above, the above method enables procedures under a reduced pressure for the first substrate and the second substrate to be conducted in different reduced pressure chambers, without the both substrates facing each other. Therefore, this method brings the following effects:
That is, the method can securely prevent water and gaseous molecules which leave one substrate from being absorbed into the other substrate. Therefore, a gas discharge panel having excellent panel properties can be obtained.
Besides, the above method enables water or the like to be removed in a condition suitable for each substrate.
Also, the above method can effectively prevent the possibility that gases due to binder burning generated from the second substrate is absorbed into the first substrate.
Further, the above method enables total surface of each substrate to be uniformly exposed to the reduced pressure.
Here, in the above-mentioned manufacturing method, after the protective layer is formed on the first substrate, the first substrate is subjected to a first substrate baking step in which the first substrate is placed under the reduced pressure and heated in the first reduced pressure chamber.
Here, in the above-mentioned manufacturing method, the second substrate is formed by a phosphor layers forming step, a phosphor layers baking step, a seal member applying step, and a seal member pre-baking step, and the second substrate is placed under the reduced pressure and heated in the second reduced pressure chamber part way through the seal member pre-baking step.
Here, in the above-mentioned manufacturing method, it is preferable that the first and the second reduced pressure chambers are each reduced to a pressure of 1,333 Pa or less.
In addition, according to the invention, a manufacturing method for a gas discharge panel that has a first substrate on which a protective layer is formed and a second substrate on which phosphor layers are formed, and the manufacturing method includes an alignment step for arranging the first substrate and the second substrate at predetermined locations, while opposing the first substrate and the second substrate, wherein the alignment step is conducted in dry gas.
Such an alignment step conducted in dry gas leads to reduction in the amount of water and gaseous molecules which are confined in the internal space in the alignment step, which suppresses problems of increase in the discharge starting voltage and generation of the abnormal discharge phenomenon and therefore realizes excellent panel properties. By the way, the internal space in the finished panel is filled with a discharge gas. Prior to the gas filling step and after the sealing step, it is difficult to effectively exhaust impurities such as water vapor from the space. Especially, when the alignment step is conducted in the air where the content of water vapor is not controlled, the difficulty becomes remarkable. However, the alignment step conducted in dry air according to the invention can reduce the amount of water vapor which is confined in the internal space in the alignment step. Therefore, a gas discharge panel having excellent panel properties can be obtained.
In addition, in the above-mentioned manufacturing method, the first substrate is placed in dry gas and heated in a first dry gas chamber and/or the second substrate is placed in dry gas and heated in a second dry gas chamber, prior to the alignment step in which the first and the second substrates are aligned in dry gas in a third dry gas chamber.
As stated above, the above method enables procedures in dry gas for the first substrate and the second substrate to be conducted in different reduced pressure chambers, without the both substrates facing each other. Therefore, this method brings the following effects:
That is, the method can securely prevent water and gaseous molecules which leave one substrate from being absorbed into the other substrate. Therefore, a gas discharge panel having excellent panel properties can be obtained.
Besides, the above method enables water or the like to be removed in a condition suitable for each substrate.
Also, the above method can effectively prevent the possibility that gases due to binder burning generated from the second substrate is absorbed into the first substrate.
Further, the above method enables total surface of each substrate to be uniformly exposed to the dry gas.
Here, in the above-mentioned manufacturing method, after the protective layer is formed on the first substrate, the first substrate is subjected to a first substrate baking step in which the first substrate is placed in dry gas and heated in the first dry gas chamber.
Here, in the above-mentioned manufacturing method, the second substrate is formed by a phosphor layers forming step, a phosphor layers baking step, a seal member applying step, and a seal member pre-baking step, and the second substrate is placed in dry gas and heated in the second dry gas chamber in the beginning of the seal member pre-baking step.
Here, in the above-mentioned manufacturing method, the first dry gas chamber and the second dry gas chamber are each filled with dry gas whose dew-point is specified to xe2x88x9230xc2x0 C. or less.
Here, in the above-mentioned manufacturing method, the first substrate is placed under the reduced pressure and heated, and the second substrate is placed in dry gas, before the alignment step is conducted.
According to the above-mentioned manufacturing methods, a gas discharge panel where a water vapor partial pressure in the internal space of the panel is 100 Pa or less can be obtained.
Since such a panel with an extremely low water vapor partial pressure inside of it can be obtained, the degree of degradation in the discharge property resulting from water is small even when an ambient temperature for the panel is decreased.
In addition, the invention relates to a manufacturing apparatus for a gas discharge panel having a first substrate carrying mechanism, a second substrate carrying mechanism, and an alignment mechanism, wherein each mechanism is provided in different hermetically sealed chambers, which each include at least one of a gas supplying mechanism and a gas exhausting mechanism.
As stated above, the above apparatus enables procedures under a reduced pressure or in dry gas for the first substrate and the second substrate to be conducted in different and sufficiently separated reduced pressure chambers, without the both substrates facing each other. Therefore, this apparatus brings the following effects:
That is, the apparatus can securely prevent water and gaseous molecules which leave one substrate from being absorbed into the other substrate. Therefore, a gas discharge panel having excellent panel properties can be obtained.
Besides, the above apparatus enables water or the like to be removed in a condition suitable for each substrate.
Also, the above apparatus can effectively prevent the possibility that gases due to binder burning generated from the second substrate is absorbed into the first substrate.
Further, the above apparatus enables total surface of each substrate to be uniformly exposed to reduced pressure or dry gas.
Here, in the above-mentioned manufacturing apparatus, connecting units are provided between the chamber including the first substrate carrying mechanism and the chamber including the alignment mechanism and between the chamber including the second substrate carrying mechanism and the chamber including the alignment mechanism, and each connecting unit has at least one of a gas supplying mechanism and a gas exhausting mechanism in it.